The project deals with olfaction and the common chemical (irritant) sense in normal persons and patients with olfactory disorders. The work will seek to improve screening tests for patients with primary olfactory complaints. Particular psychophysical experiments will focus upon a new adaptive method for measurement of odor threshold in the clinic and a new test of odor identification predicated upon measurement of odor quality discrimination. A hand-held olfactometer for widespread screening of olfactory functioning will be subjected to both chemical and psychophysical scrutiny. Psychophysical tests with more analytical goals than those needed for simple screening will be devised to evaluate facets of processing in patients with secondary olfactory dysfunction. Such testing, which will include odor memory, odor hedonics, will focus on the interface between will be to develop tests for use to evaluate olfactory processing in patients with central neurological disorders and some dementia, such as Alzheimers disease and Huntington's disease. As with the portable olfactometer, the availability of such tests may broaden the study and evaluation of olfaction by professionals who do not now specialize in it. Investigation of the common chemical sense will focus on measurement of pure nasal irritation in patients with olfactory loss (anosmics). Threshold and reaction time data collected on homologous chemical series from such persons can shed light on the physicochemical basis for irritation. Stimuli of interest also will include substances implicated in indoor air pollution and some of the experiments will relate directly to matters of both indoor and outdoor air pollution (e.g., whether mixtures of chemicals individually at subthreshold levels of irritation can together trigger irritation and whether nasal inflammation causes perceptual hypersensitivity). The research will also extend to a subpopulation of persons with multiple chemical sensitivities in order to test the whether such persons may prove hypersensitive to irritation and may have hyperreactive lower airways. Tests on such persons will include olfactory assessment, common chemical sense assessment, and pulmonary function testing with methacholine challenge. A series of studies will also delve into early temporal events in human olfaction and possible facilitatory effects of odorant-binding protein, a substance that may enhance the speed at which odorants reach olfactory receptors and free nerve endings of the common chemical sense. Such studies will entail measurement of reaction time, threshold, and temporal modulation of olfactory and common chemical stimulation.